/* Libiberty realpath.  Like realpath, but more consistent behavior.
   Based on gdb_realpath from GDB.

   Copyright 2003 Free Software Foundation, Inc.

   This file is part of the libiberty library.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street - Fifth Floor,
   Boston, MA 02110-1301, USA.  */

/*

@deftypefn Replacement {const char*} lrealpath (const char *@var{name})

Given a pointer to a string containing a pathname, returns a canonical
version of the filename.  Symlinks will be resolved, and ``.'' and ``..''
components will be simplified.  The returned value will be allocated using
@code{malloc}, or @code{NULL} will be returned on a memory allocation error.

@end deftypefn

*/

#include "config.h"
#include "lrealpath.h"

#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif

/* On GNU libc systems the declaration is only visible with _GNU_SOURCE.  */
#if defined(HAVE_CANONICALIZE_FILE_NAME) && defined(NEED_DECLARATION_CANONICALIZE_FILE_NAME)
extern char* canonicalize_file_name(const char*);
#endif

#if defined(HAVE_REALPATH)
#if defined(PATH_MAX)
#define REALPATH_LIMIT PATH_MAX
#else
#if defined(MAXPATHLEN)
#define REALPATH_LIMIT MAXPATHLEN
#endif
#endif
#else
/* cygwin has realpath, so it won't get here.  */
#if defined(_WIN32)
#define WIN32_LEAN_AND_MEAN
#include <windows.h> /* for GetFullPathName */
#endif
#endif

char*
lrealpath(const char* filename) {
    /* Method 1: The system has a compile time upper bound on a filename
       path.  Use that and realpath() to canonicalize the name.  This is
       the most common case.  Note that, if there isn't a compile time
       upper bound, you want to avoid realpath() at all costs.  */
#if defined(REALPATH_LIMIT)
    {
        char        buf[REALPATH_LIMIT];
        const char* rp = realpath(filename, buf);
        if (rp == NULL)
            rp = filename;
        return strdup(rp);
    }
    /* REALPATH_LIMIT */

    /* Method 2: The host system (i.e., GNU) has the function
       canonicalize_file_name() which malloc's a chunk of memory and
       returns that, use that.  */
#elif defined(HAVE_CANONICALIZE_FILE_NAME)
    {
        char* rp = canonicalize_file_name(filename);
        if (rp == NULL)
            return strdup(filename);
        else
            return rp;
    }
    /* HAVE_CANONICALIZE_FILE_NAME */

    /* Method 3: Now we're getting desperate!  The system doesn't have a
       compile time buffer size and no alternative function.  Query the
       OS, using pathconf(), for the buffer limit.  Care is needed
       though, some systems do not limit PATH_MAX (return -1 for
       pathconf()) making it impossible to pass a correctly sized buffer
       to realpath() (it could always overflow).  On those systems, we
       skip this.  */
#elif defined(HAVE_REALPATH) && defined(HAVE_UNISTD_H)
    {
        /* Find out the max path size.  */
        long path_max = pathconf("/", _PC_PATH_MAX);
        if (path_max > 0) {
            /* PATH_MAX is bounded.  */
            char *buf, *rp, *ret;
            buf = (char*)malloc(path_max);
            if (buf == NULL)
                return NULL;
            rp  = realpath(filename, buf);
            ret = strdup(rp ? rp : filename);
            free(buf);
            return ret;
        } else {
            return NULL;
        }
    }
    /* HAVE_REALPATH && HAVE_UNISTD_H */

    /* The MS Windows method.  If we don't have realpath, we assume we
       don't have symlinks and just canonicalize to a Windows absolute
       path.  GetFullPath converts ../ and ./ in relative paths to
       absolute paths, filling in current drive if one is not given
       or using the current directory of a specified drive (eg, "E:foo").
       It also converts all forward slashes to back slashes.  */
#elif defined(_WIN32)
    {
        char  buf[MAX_PATH];
        char* basename;
        DWORD len = GetFullPathName(filename, MAX_PATH, buf, &basename);
        if (len == 0 || len > MAX_PATH - 1)
            return strdup(filename);
        else {
            /* The file system is case-preserving but case-insensitive,
               Canonicalize to lowercase, using the codepage associated
               with the process locale.  */
            CharLowerBuff(buf, len);
            return strdup(buf);
        }
    }
#else

    /* This system is a lost cause, just duplicate the filename.  */
    return strdup(filename);
#endif
}
